A stent is an elongated device used to support an intraluminal wall. In the case of a stenosis, a stent provides an unobstructed conduit through a body lumen in the area of the stenosis. Such a stent may also have a prosthetic graft layer of fabric or covering lining the inside and/or outside thereof. Such a covered stent is commonly referred to in the art as an intraluminal prosthesis, an endoluminal or endovascular graft (EVG), or a stentgraft. A stent-graft may be used, for example, to treat a vascular aneurysm by removing the pressure on a weakened part of an artery so as to reduce the risk of rupture. Other devices, such as filters, particularly vena cava filters, may have similar structures to stents and may be placed in a body lumen by similar methods. As used herein, the term “endoluminal device” refers to covered and uncovered stents, filters, and any other device that may be placed in a lumen. The term “stent” as used herein is a shorthand reference referring to a covered or uncovered stent.
Typically, an endoluminal device, such as a stent-graft deployed in a blood vessel at the site of a stenosis or aneurysm, is implanted endoluminally, i.e. by so-called “minimally invasive techniques” in which the device, restrained in a radially compressed configuration by a sheath or catheter, is delivered by a delivery system or “introducer” to the site where it is required. The introducer may enter the body from an access location outside the body, such as through the patient's skin, or by a “cut down” technique in which the entry blood vessel is exposed by minor surgical means. The term “proximal” as used herein refers to portions of the stent or delivery system relatively closer to this access location, whereas the term “distal” is used to refer to portions farther from the access location.
When the introducer has been threaded into the body lumen to the stent deployment location, the introducer is manipulated to cause the stent to be ejected from the surrounding sheath or catheter in which it is restrained (or alternatively the surrounding sheath or catheter is retracted from the stent), whereupon the stent expands to a predetermined diameter at the deployment location, and the introducer is withdrawn. Stent expansion may be effected by spring elasticity, balloon expansion, or by the self-expansion of a thermally or stress-induced return of a memory material to a pre-conditioned expanded configuration.
Referring now to a typical prior art introducer as seen in FIGS. 1A and 1B, there is shown a standard pre-loaded delivery system 10 comprising an outer sheath 12, a compressed endoluminal device 14 loaded therein, and a conventional stabilizer 16 loaded adjacent to the proximal end 17 of the endoluminal device. A standard deployment technique comprises maneuvering the introducer to a desired deployment location and retracting outer sheath 12 so that the endoluminal device is deployed beginning at its distal end and ending at its proximal end. Stabilizer 16 stabilizes or prevent retraction of endoluminal device 14 when sheath 12 is retracted, thus effecting deployment of the device into a desired location by forcing relative movement between the sheath and the device.
Delivery system 10 also may comprise a catheter tip 20 at its distal end attached to an internal shaft 23 that runs through the delivery system through inner lumen 22 in stabilizer 16, as shown in FIG. 1A. A stabilizer handle 26 is typically located at the proximal end of stabilizer 16, outside the body lumen. Internal shaft 23 may guide the delivery system through the body lumen over a guidewire (not shown) to the area to be repaired, or may be adapted for inflating a balloon (if applicable), and/or for flushing the system.
It is often important during endoluminal device delivery to ensure accurate placement of the device termini, particularly in intravascular deployment of multipart stents. Improper stent placement can prevent successful medical treatment. There is a particular need in the art to anchor the proximal end of a self-expanding stent while deploying the distal end, and also to provide accurate deployment of self-expanding stents in a way that prevents recoil of the endoluminal device upon release, which may adversely affect the accuracy of the device placement. Balloons are commonly used to anchor endoluminal devices during deployment, but the pressure of a balloon against a vessel wall may damage tissue, particularly if the vessel wall is already diseased. Thus, it is further desirable to anchor the proximal end of an endoluminal device while deploying the distal end without applying unnecessary force against the vessel wall.
In a procedure to repair an abdominal aortic aneurysm (AAA), use of a modular self-expanding stent involves accurate placement of a terminus of a first stent component in the abdominal aorta just below the renal arteries. A second stent component is then deployed in the first stent component and permitted to extend to a terminus in one of the iliac arteries. It is difficult, however, to ensure accurate placement of the iliac terminus of the second stent component. If the terminus is not placed far enough into the iliac, then the stent may be ineffective. If the terminus extends too far, it may interfere with blood flow in arteries branching from the iliac, such as the internal iliac artery. This problem also occurs in the deployment of multipart stents in other branched arteries. Thus, it is desirable to provide a way to ensure accurate deployment of all the termini of a multipart stent.